1. Field of the Invention
The present invention relates to an acceleration sensor for detecting acceleration in three orthogonal directions.
2. Description of the Related Art
Various acceleration sensors have been proposed for detecting acceleration in three-dimensional directions, i.e. along X-axis, Y-axis and Z-axis. Japanese patent application “Kokai” No. 10-10150 cited herein as Document 1 (FIGS. 1 to 3, and paragraphs 7 to 22), for example, discloses an acceleration sensor for detecting acceleration based on variations in capacitance between a fixed electrode and a movable electrode opposed to each other. According to this technique, one of the fixed electrode and movable electrode has an electret film formed on a surface thereof opposed to the other electrode. The movable electrode has a weight attached to a surface thereof facing away from the fixed electrode to allow for displacement of the movable electrode in time of impression of acceleration. The other electrode not having the electret film is divided along orthogonal axes crossing one another at an intersection corresponding to a position of projection of the center of gravity of the weight. That is, with one of the electrodes divided, acceleration along a plurality of axes is detected based on variations in capacitance of the divided electrode.